This proposal aims to address a fundamental issue in biology-how signals between cells of different organisms can generate a specific behavior. To elaborate an appropriate behavioral response , an animal must perceive cues from its environment, transduce these signals and integrate them. The relevance of this issue is at the core of basic neurobiology, yet the study of behavior is quite complex. To simplify the task I will be studying a stereotyped behavior in an invertebrate system with a small well-defined nervous system. More specifically, this proposal investigates the neuronal mechanisms underlying the initiation of the male mating sub-behavior of sperm transfer in C. elegans. I will be focusing on the hermaphrodite sensory cues necessary for sperm transfer from the male, as well as the pathways involved in perception of these signals by the male. These questions will be investigated by means of surgical and genetic methods.